Methods for controlling a service session handover between network slices, network nodes and a communications device implementing the methods in a communications network

This application is a national-phase entry under 35 USC § 371 of International Application No. PCT/SE2021/050756, filed Jul. 27, 2021, titled “Methods for Controlling a Service Session Handover Between Network Slices, Network Nodes and a Communications Device Implementing the Methods in a Communications Network,” the contents of which are hereby incorporated herein in its entirety.

The embodiments herein relate to methods for controlling a service session handover between network slices and network nodes and a communications device implementing the methods in a communications network. A corresponding computer program and computer program carrier are also disclosed.

In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or User Equipment (UE), communicate via a Local Area Network such as a Wi-Fi network or a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio access node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in 5G. A service area or cell area is a geographical area where radio coverage is provided by the radio access node. The radio access node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio access node.

Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to evolve the specifications of the Fifth Generation (5G) network also referred to as 5G New Radio (NR). The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio access nodes are directly connected to the EPC core network rather than to RNCs used in 3G networks. In general, in E-UTRAN/LTE the functions of a 3G RNC are distributed between the radio access nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio access nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio access nodes, this interface being denoted the X2 interface.

Wireless Communication Systems in 3GPP

1 FIG. 1 FIG. 12 103 104 106 103 104 10 illustrates a simplified wireless communication system. Consider the simplified wireless communication system in, with a UE, which communicates with one or multiple access nodes-, which in turn are connected to a network node. The access nodes-are part of a radio access network.

103 104 106 10 For wireless communication systems pursuant to 3GPP Evolved Packet System, (EPS), also referred to as Long Term Evolution, LTE, or 4G, standard specifications, such as specified in 3GPP TS 36.300 and related specifications, the access nodes-corresponds typically to Evolved NodeBs (eNBs) and the network nodecorresponds typically to either a Mobility Management Entity (MME) and/or a Serving Gateway (SGW). The eNB is part of the radio access network, which in this case is the E-UTRAN (Evolved Universal Terrestrial Radio Access Network), while the MME and SGW are both part of the EPC (Evolved Packet Core network). The eNBs are inter-connected via the X2 interface, and connected to EPC via the S1 interface, more specifically via S1-C to the MME and S1-U to the SGW.

2 FIG. illustrates a 5G reference architecture as defined by 3GPP.

103 104 203 106 206 206 203 10 206 206 12 206 1 FIG. 1 FIG. 2 FIG. a b a b a. For wireless communications systems pursuant to the 3GPP 5G System, 5GS (also referred to as New Radio, NR, or 5G) standard specifications, such as specified in 3GPP TS 38.300 and related specifications, on the other hand, the access nodes-ofcorrespond typically to a 5G NodeB (gNB) of a 5G Access Network (AN)and the network nodecorresponds typically to either an Access and Mobility Management Function (AMF)and/or a User Plane Function (UPF). The 5G ANmay be a Radio Access Network (RAN) corresponding to the radio access networkof. In the 5G case the RAN is called NG-RAN (Next Generation Radio Access Network). The AMFand UPFare both part of the 5G Core Network (5GC). The gNBs may be inter-connected via an Xn interface, and connected to 5GC via the NG interface, more specifically via NG-C to the AMF and NG-U to the UPF. Inthe NG-U interface is referred to as N3, while the NG-C interface is referred to as N2 in line with 3gpp terminology. An interface N1 is arranged between the UEand the AMF

203 12 2 FIG. The ANmay further comprise an Access Gateway (AGW) (not shown in) which acts essentially as the Mobile IP client on behalf of the UE.

To support fast mobility between NR and LTE and avoid change of core network, LTE eNBs can also be connected to the 5G-CN via NG-U/NG-C and support the Xn interface. An eNB connected to 5GC is called a next generation eNB (ng-eNB) and is considered part of the NG-RAN. LTE connected to 5GC will not be discussed further in this document; however, it should be noted that most of the solutions/features described for LTE and NR in this document also apply to LTE connected to 5GC. In this document, when the term LTE is used without further specification it refers to LTE-EPC.

2 FIG. 220 220 12 further comprises an Application Function (AF)that interacts with the 3GPP Core Network in order to provide services, for example to support interactions between the 5GC and an Internet Protocol (IP) Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS). Thus, the AFmay support IP-based multimedia services for the UE.

The IMS is a standardized architectural framework for delivering IP-based multimedia services. Historically, mobile phones have provided voice call services over a circuit-switched-style network, rather than strictly over an IP packet-switched network. However, now alternative methods of delivering voice, e.g., Voice over IP (VoIP), or other multimedia services have become available. VoIP over a 5G network may also be referred to as Vo5G or Voice over NR (VoNR).

220 206 12 203 12 d A Proxy Call Session Control Function (P-CSCF) in the role of the AFmay interact with the Policy and Charging Architecture of the 5GC, for example with a Policy and Charging Function (PCF). The P-CSCF may be a first contact point within the IP Multimedia Core Network (IM CN) subsystem and it may ensure that relevant Session Initiation Protocol (SIP) messages contain the correct or up to date information about a user location information of the UEprovided by the access networkcurrently used by the UE.

206 206 206 d d d The SIP is a signaling protocol used for initiating, maintaining, and terminating real-time sessions that include voice, video and messaging applications. SIP is for example used for signaling and controlling multimedia communication sessions in applications of Internet telephony for voice and video calls, in private IP telephone systems, in instant messaging over IP networks as well as mobile phone calling over LTE (VoLTE). The 5G System architecture supports an N5 interface between the PCFand the P-CSCF and also supports an Rx interface between the PCFand the P-CSCF, to enable IMS service. Rx support between the PCFand the P-CSCF may be needed for backwards compatibility for early deployments using Diameter between the IMS and the 5GC functions.

206 206 206 206 206 206 d d c c d c The PCFsupports a unified policy framework to govern the network behavior. Specifically, the PCFmay provide Policy and Charging Control (PCC) rules to a Session Management Function (SMF)together with an authorized Quality of Service (QoS) to be enforced by the SMF. Further, the PCFmay request access network information, including user location information, from the SMFand reports the received access network information, including the user location information, to the P-CSCF.

206 206 206 206 206 206 c c d d c b. The SMFsupports different functionalities. Specifically, the SMFmay receive PCC rules from the PCFover an N7 interface, enforce the authorized QoS and report the access network information to the PCFas mentioned above. Further, the SMFmay have an N4 interface to the UPF

The IMS may further comprise a multimedia application server, such as a Multimedia Telephony Application Server (MTAS).

The IMS may further comprise other types of CSCFs, e.g., a Serving CSCF (S-CSCF) and an Interrogating CSCF (I-CSCF).

The IMS may further comprise an access transfer gateway (ATGW) that provides an anchor point for a data stream, such as a Real-time Transport Protocol (RTP) stream.

3 FIG. 200 200 12 12 200 200 203 206 210 200 203 206 210 a b a b b a a a a b b b b. illustrates two 5G reference architectures, an originating 5G networkand a terminating 5G networkinvolved in an IMS session, such as a VoIP session. An originating UEin the originating 5G network calls a terminating UEin the terminating 5G network. The originating networkcomprises an originating AN, an originating CNand an originating IMS. The terminating networkcomprises a terminating AN, a terminating CNand a terminating IMS

12 12 12 Embodiments herein relate to IMS and therefore a brief overview of a procedure for establishing an IMS session will first be given. First the UEattaches to a communications network, such as a 5G network. For example, the UEmay make an NR Attach to an NR access network. Then a default PDU session for IMS is established with the communications network, e.g., with the core network. Then a default IMS session is established with the communications network. The default IMS session may have certain restrictions, such as a maximum bandwidth. Finally, the UEmakes a SIP/IMS registration in the IMS, that is with an application function of the communications network. Then a dedicated IMS session to for example a second UE may be established. For the dedicated IMS session also a subscription of the UE may put certain other restrictions on the dedicated IMS session.

4 FIG. illustrates the concept of dividing a communications network into network slices. Each network slice may be identified by a corresponding network slice identifier, such a Single Network Slice Selection Assistance Information (S-NSSAI).

4 FIG. 4 FIG. 4 FIG. 12 1 2 3 further illustrates how different network slices may provide different services to the UE. Network slices may be optimized for network performance for the services expected to run over them. Services running in these network slices may be IMS and/or non-IMS services as illustrated in.illustrates three 5GC slices: 1) a first network slice NSmay be adapted for Mobile Broadband (eMBB) and may be used for a non-IMs service and a first IMS service, 2) as second network slice NSmay be adapted for Mission Critical services (MC) and may be used for a second IMS service, 3) a third network slice NSmay be adapted for Vehicle-to-everything (V2X) and may be used for a third IMS service and a non-IMS service.

Thus, it is feasible to have numerous IMS services running on different network slices, some IMS services are the same some are different. This may be due to various factors such as an optimized 5GC slice for the IMS service or just convenience. For example, a VoLTE session may run on a network slice for eMBB or even on a network slice for Vehicle-to-Vehicle (V2V). IMS is agnostic to network slices.

12 It may be the case that an IMS session established over one 5GC slice needs to be transferred seamlessly to another 5GC slice. This may be due to several factors such as the need to terminate a 5GC slice completely because it is no longer needed as the main non-IMS application is completed, and the IMS session over that 5GC slice may be transferred to another 5GC slice. Or the 5GC slice may be draining the battery power of the UEas well.

An object of embodiments herein may be to obviate some of the problems related to handling service sessions on network slices. Specifically to obviate some of the problems related to service session handover between network slices, or at least reduce the impact of them.

Embodiments herein enable a seamless handover of a service session, such as an IMS session between network slices, e.g., a VoLTE session from one 5GC slice to another.

According to a first aspect, the object is achieved by method for controlling a service session handover between network slices. The service session may be a multimedia session, for example an IMS session.

The method comprises establishing a first default data session on a first network slice of a communications network based on a first network slice identifier of the first network slice such that a first network address of the first communications device, a first application node of an application layer system, and a first access gateway of the application layer system is associated with the first default data session.

The method further comprises establishing an associated first dedicated service session with a second communications device over a first dedicated data session based on the first default data session on the first network slice.

The method further comprises establishing a second default data session over a second network slice of the communications network based on a second network slice identifier of the second network slice such that a second network address of the first communications device, a second application node of the application layer system, and a second access gateway of the application layer system is associated with the second default data session.

The method further comprises sending a session controlling message to the first application node. The session controlling message controls the service session. The session controlling message may be a SIP message. The session controlling message comprises: the second network address of the first communications device, a network address of the second application node, and a session identifier of the first dedicated service session, to enable reserving network resources of the second access gateway for a second dedicated service session between the first communications device and the second communications device established over a second dedicated data session based on the second default data session on the second network slice such that handover of the first dedicated service session between the first network slice and the second network slice is enabled.

According to a second aspect, the object is achieved by a communications device. The communications device is configured to perform the method according to the first aspect.

According to a third aspect, the object is achieved by a method, performed by a first application node of an application layer system controlling service sessions, for controlling a service session handover between network slices.

The method comprises establishing a first dedicated service session between a first communications device and a second communications device established over a first dedicated data session based on a first default data session of the first communications device on a first network slice of a communications network.

The method further comprises receiving, from the first communications device, a session controlling message comprising: a second network address of the first communications device, a network address of a second application node associated with a second default data session of the first communications device established over a second network slice of the communications network, and a session identifier of the first dedicated service session, to enable reserving network resources of a second access gateway for a second dedicated service session between the first communications device and the second communications device established over a second dedicated data session based on the second default data session on the second network slice such that handover of the first dedicated service session between the first network slice and the second network slice is enabled.

a) the second network address of the first communications device, b) a context of the first dedicated service session, to enable the second application node to perform network resource reservation and establish a data path with the second communications device for the second dedicated service session between the first communications device and the second communications device, such that handover of the first dedicated service session between the first network slice and the second network slice is enabled. c) a network address of an access gateway serving the second communications device, Based on the contents of the received session controlling message the method further comprises sending a second session controlling message to the second application node, comprising:

According to a fourth aspect, the object is achieved by a first application node. The first application node is configured to perform the method according to the third aspect.

According to a fifth aspect, the object is achieved by a method, performed by a second application node of an application layer system, for controlling a service session handover between a first network slice and a second network slice.

The method is at least partly performed during a first dedicated service session between a first communications device and a second communications device established over a first dedicated data session based on a first default data session of the first communications device on the first network slice of a communications network comprising the first and the second network slices. The first default data session is based on a first network slice identifier such that a first network address of the first communications device, a first application node of the application layer system, and a first access gateway of the application layer system is associated with the first default data session.

The method comprises registering the first communications device in the application layer system for a second default service session to be established over a second default data session, based on a second network slice identifier such that a second network address of the first communications device, the second application node, and a second access gateway is associated with the second default service session.

a) the second network address of the first communications device; b) a context of the first dedicated service session; c) a network address of an access gateway serving the second communications device, to enable the second application node to perform network resource reservation and establish a data path with the second communications device for a second dedicated service session between the first communications device and the second communications device established over a second dedicated data session based on the second default data session on the second network slice, such that handover of the first dedicated service session between the first network slice and the second network slice is enabled. The method further comprises receiving, from a first application node associated with the first network slice and controlling the first dedicated service session, a session controlling message. The session controlling message comprises:

The method further comprises reserving network resources of the second access gateway for the first dedicated service session to be transferred to the second dedicated service session based on the received session controlling message.

The method further comprises sending to the first application node a second session controlling message with information related to the reserved network resources of the second access gateway.

According to a sixth aspect, the object is achieved by a second application node. The second application node is configured to perform the method according to the fifth aspect.

According to a seventh aspect, the object is achieved by a computer program comprising instructions, which when executed by a processor, causes the processor to perform actions according to any of the aspects above.

According to an eighth aspect, the object is achieved by a carrier comprising the computer program of the aspect above, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

Since the session controlling message, transmitted from the communications device to the first application node, comprises the second network address of the first communications device, the network address of the second application node, and the session identifier of the first dedicated service session, reservation of network resources of the second access gateway for the second dedicated service session between the first communications device and the second communications device is enabled such that handover of the first dedicated service session between the first network slice and the second network slice is enabled.

A further advantage of embodiments herein is that they enable seamless handover of a service session.

A further advantage of embodiments herein is that they provide flexibility for IMS integration with 5GC offered capabilities.

As mentioned above, an object of embodiments herein may be to obviate some of the problems related to service session handover between network slices, or at least reduce the impact of them. The service session may for example be an IMS service session, such as a voice service session.

5 a FIG. 3 FIG. 5 a FIG. 500 500 200 500 503 500 1 2 500 a a a a a a a a a Embodiments herein relate to communications networks in general.is a schematic overview depicting a communications network, such as a first communications networkwherein embodiments herein may be implemented. The first communications networkmay correspond to the originating networkof. The first communications networkcomprises one or more access networks, such as a first ANand one or more CN. The CN of the first communications networkmay be functionally divided into network slices, such as a first network slice NSand a second network slice NS. A 5G network architecture has been used into illustrate the first communications network. In the following description embodiments will be described with reference to this 5G reference architecture. However, embodiments are also applicable to other network architectures, in particular to other network architectures that support network slicing or something similar to network slicing.

500 1 506 1 206 506 1 206 506 1 1 506 1 206 506 1 206 206 206 206 206 a c a c d a d d a a a a b a b c d a b 2 FIG. Each network slice of the first communications networkcomprises one or more CN nodes. For example, the first network slice NSmay comprise a first session management node_implementing the SMFand a first policy controlling node_implementing the PCF. The first policy controlling node_may besides handling policies for resource reservation also handle charging. The first network slice NSmay further comprise a first access and mobility management node_implementing the AMFand a first user plane node_implementing the UPF. The SMF, the PCF, the AMFand the UPFwere all described above in relation to.

2 506 2 506 2 2 506 2 506 2 c a d a a a b a The second network slice NSmay comprise a second session management node_and a second policy controlling node_. The second network slice NSmay further comprise a second access and mobility management node_and a second user plane node_.

506 1 506 2 506 1 506 2 506 1 506 2 c a c a a a a a b a b a In a 4G-embodiment the session management nodes_,_and the access and mobility management nodes_,_may be implemented by a Mobility Management Entity (MME). The user plane nodes_,_may be implemented by a Packet Data Network Gateway (PDN-GW) in 4G.

The CN nodes may be logical nodes for performing the above-mentioned CN functions which each may be implemented in one or more physical nodes or devices.

500 503 a a The first communications networkmay be a wireless communications network, or a communications network supporting wireless and wireline convergence, such as 5G Wireless Wireline Convergence. Then the first ANmay comprise one or more RANs. The wireless communications network may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, 5G, New Radio (NR), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments herein relate to recent technology trends that are of particular interest in a 5G context. However, embodiments are also applicable in further development of the existing wireless communications systems such as e.g. LTE.

500 a Access nodes operate in the first communications network, such as a radio access node. The radio access node provides radio coverage over a geographical area, a service area referred to as a cell, which may also be referred to as a beam or a beam group of a first radio access technology (RAT), such as 5G, LTE, Wi-Fi or similar. The radio access node may be a NR-RAN node, transmission and reception point e.g. a base station, a radio access node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a gNB, a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of communicating with a wireless device within the service area depending e.g. on the radio access technology and terminology used. The respective radio access node may be referred to as a serving radio access node and communicates with a UE with Downlink (DL) transmissions to the UE and Uplink (UL) transmissions from the UE.

500 512 512 12 512 512 a a a a a a 3 FIG. A number of communications devices operate in the first communications network, such as a first communications device. The first communications devicemay correspond to the originating UEof. The first communications devicemay be a wireless communications device. Further, the first communications devicemay be a mobile station, a non-access point (non-AP) STA, a STA, a user equipment (UE) and/or a wireless terminal, that communicate via one or more Access Networks (AN), e.g. RAN, e.g. via the radio access node to one or more CNs.

503 10 512 506 1 503 506 1 503 506 1 506 1 506 1 506 1 521 1 506 1 506 1 506 506 1 1 2 a a a a a a a a b a b a c a d a a c a d a a c a 1 FIG. 5 a FIG. 2 FIG. 5 a FIG. The 5G first ANmay be a Radio Access Network (RAN) corresponding to the radio access networkof. In the 5G case the RAN is called NG-RAN (Next Generation Radio Access Network). The gNBs may be inter-connected via an Xn interface, and connected to 5GC via the NG interface, more specifically via NG-C to the AMF and NG-U to the UPF. The interfaces between the nodes ofcorrespond to the interfaces of. Specifically,shows a first interface N1 between the first communications deviceand the first access and mobility management node_, a second interface N2 between the first ANand the first access and mobility management node_, a third interface N3 between the first ANand the first user plane node_, a fourth interface N4 between the first user plane node_and the first session management node_, a fifth interface N5 between the first policy controlling node_and the first application nodeand a further interface N7 between the first session management node_and the first policy controlling node_. The first access and mobility management nodeal may further be interfaced to the first session management node_with an interface referred to as N11. The same interfaces as defined for the network slice NSmay also be defined for the second network slice NS.

5 b FIG. 3 FIG. 500 500 200 500 500 500 503 b b b b a b b illustrates a second communications networkwherein embodiments herein may be implemented. The second communications networkmay correspond to the terminating networkof. The second communications networkmay comprise components corresponding to the components of the first communications network. In particular, the second communications networkcomprises one or more access networks, such as a second ANand one or more CNs, such as a second CN.

500 1 500 500 500 500 b b b b b b 5 b FIG. The CN of the second communications networkmay be functionally divided into network slices, such as a first network slice NSof the second communications networkand a second network slice of the second communications network. For simplicity, the second network slice of the second communications networkis not illustrated in. Each network slice of the second communications networkcomprises one or more CN nodes.

500 b The second communications networkmay be a wireless communications network or a communications network supporting wireless and wireline convergence, such as 5G Wireless Wireline Convergence.

500 512 512 12 512 500 500 b b b b b a b. 3 FIG. A number of communications devices operate in the second communications network, such as a second communications device. The second communications devicemay correspond to the terminating UEof. The second communications devicemay be a wireless communications device. The same interfaces as defined for the first communications networkmay also be defined for the second communications network

500 500 b a. In some embodiments the second communications networkis the same communications network as the first communications network

5 5 a b FIGS.and 520 500 520 500 520 520 500 500 520 520 520 520 a a b b a b a b a b a b further illustrate an application layer system, such as a first application layer system, also referred to herein as a first application network, associated with or comprised in the first communications network, and a second application layer system, also referred to herein as a second application network, associated with the second communications network. The respective application network,is connected to the respective CN of the respective communications network,. The application network may be an IMS. The application network,comprises one or more application functions, such as the P-CSCF and IMS core functions, such as Serving-Call Session Control Function (S-CSCF), Interrogating-Call Session Control Function I-CSCF, and IMS Application Servers. The application network,further comprises an ATGW that provides an anchor point for a data stream, such as an RTP stream. The ATGW may be co-located with the P-CSCF.

520 520 521 1 522 1 523 1 512 523 1 521 522 523 1 512 512 a a a a a a a a a a a b. The first application networkcomprises one or more application nodes. Some of the applications nodes may be associated with a specific network slice. For example, the first application networkmay comprise a first application nodeand a first core application nodeand a first access gatewayfor providing a service for the first communications device. The first access gatewaymay be implemented as an ATGW. For example, the first application nodeand the first core application nodeand the first access gatewaymay each control different aspects of a service session delivering the service, such as an IMS session delivering a voice call, between the first communications deviceand the second communications device

521 523 1 1 521 2 523 2 2 523 2 520 522 2 a a a a a a a The first application nodeand the first access gatewaymay be associated with the first network slice NS, while a second application nodeand a second access gatewaymay be associated with the second network slice NS. The second access gatewaymay be implemented as an ATGW. The first application networkmay further comprise a second core application node. The core application nodes are not necessarily associated with a specific network slice.

520 512 b b. The second application networkalso comprises one or more application nodes corresponding to the above-mentioned application nodes for providing a service for the second communications device

521 1 521 2 522 1 522 2 a a a a For example, the P-CSCF may be implemented by the first and the second application nodes,, while an IMS core function, such as the S-CSCF, may be implemented by the first and second core application nodes,. In general, the one or more application nodes may be logical nodes for performing the above-mentioned application functions. Each application node may be implemented in one or more physical nodes or devices.

520 520 a b. The IMS may further comprises a multimedia application server, such as a first multimedia application server in the first application networkand a second multimedia application server in the second application network

Generally, an application function interacts with the CN to provide specific services, such as voice, video, gaming, and VR, and may affect routing and/or policy decisions affecting quality of service. An example of an application function is IMS providing voice and video calling services.

512 512 500 500 512 512 530 530 506 506 512 512 500 a b a b a b a b b a b b a b b. The service may be provided to the communications device,through the CN of the communications network,. For example, the service may be provided over a data session, such as a Protocol Data Unit (PDU) session. The data session provides end-to-end user plane connectivity between the communications device,and a specific Data Network,through the user plane node_,_. For example, for voice over IMS a PDU session for IMS voice may provide end-to-end user plane connectivity between the first communications deviceand the second communications devicein the second communications network

A data session, such as a PDU Session, may support one or more QoS Flows. There may be a one-to-one mapping between QoS Flow and QoS profile. For example, for 5G the one-to-one mapping between QoS Flow and QoS profile means that all packets belonging to a specific QoS Flow may have the same 5QI.

506 1 506 2 c a c a The session management nodes_,_may control the service session and the associated data session through the N4 interface.

It should be understood by the skilled in the art that “communications device” and “UE” are non-limiting terms which mean any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station communicating within a cell.

512 521 1 521 2 a a a Methods herein may in a first aspect be performed by the first communication device, and in a second aspect by the first application node, and in a third aspect by the second application node.

540 540 a b 5 a FIG. 5 b FIG. As an alternative, a Distributed Node (DN) and functionality, e.g. comprised in a first cloudas shown in, or a second cloudas shown in, may be used for performing or partly performing the methods.

521 1 521 2 a a In the cloud implementation, the functions of anyone or all of the first application nodeand the second application node, may be deployed in a virtualized environment. The signaling sequences between the nodes or functions does not change if some or all of them are deployed in the cloud.

6 6 a b FIGS.and 7 7 a c FIGS.- 7 7 a c FIGS.- 7 a FIG. 7 b FIG. 7 7 a c FIGS.and 512 521 1 521 2 512 1 512 2 500 500 a a a a a a b Exemplifying methods for controlling a service session handover between network slices according to embodiments herein will now be described with reference toand the combined signalling diagrams and flow charts ofdescribing interaction between the first communications device, the first application nodeand the second application node. The combined signalling diagrams and flow charts ofalso illustrates interaction between the first communications deviceand the first network slice NS(), and interaction between the first communications deviceand the second network slice NS(), and interactions between the first communications networkand the second communications network(). It is to be noted that all nodes that may interact in the methods described below are not shown for simplicity.

5 5 a b FIGS.and The exemplifying methods will also be described with further reference to. The embodiments will be described based on a 5G architecture combined with an IMS. The data session will be exemplified with a PDU IMS session, that is a PDU session for IMS services.

6 6 7 7 a b a c FIGS.,and- 521 1 521 2 522 1 522 2 a a a a Inthe communications devices will be exemplified with UEs, the first and second application nodes,with P-CSCFs and the first and second core application nodes,with S-CSCFs.

6 a FIG. 1 2 1 521 1 521 1 522 1 a a a illustrates a typical example of a UE with two different network slices NS, NSand where each network slice is used to set up some IMS services. The first network slice NS, used for eMBB, is associated with the first application node. The first application nodeis associated with a first core application node.

2 521 2 522 2 a a The second network slice NS, used for MC, is associated with the second application nodeand a second core network node.

1 521 1 522 1 2 521 1 522 2 a a a a Different services are indicated with different types of lines between the nodes. A first service, indicated with a solid line, is run over the first network slice NS, the first application nodeand the first core application node. A second service, indicated with a hatched-dotted line, is run over the second network slice NS, the first application nodeand the second core application node.

2 1 The UE may want to transfer one of the IMS sessions to the second network slice NSfor MC so that it may terminate the first network slice NSfor eMBB.

1 1 2 2 Further, a first network slice identifier S-NSSAI_identifies the first network slice NS, while a second network slice identifier S-NSSAI_identifies the second network slice NS.

6 b FIG. 2 1 illustrates how the first service has been handed over to the second network slice NS, and where the first network slice NSis terminated. It can be seen that the P-CSCF has changed, but the same S-CSCF being used before is maintained.

7 7 a c FIGS.- 512 512 a b The exemplifying methods disclosed in connection withare described with the assumption that a regular first IMS session, such as a voice session, is first established, then one of the first and second communications devices,initiates service session handover between network slices.

500 500 a b It is further assumed that the first communications networkrepresents the originating side and the second communications networkrepresents the terminating side. The following may be a description of actions in a call flow.

7 7 a c FIGS.- show a detailed call flow for seamlessly handing over an IMS session from one network slice to another.

7 a FIG. illustrates setting up the first IMS session and the first media path for the IMS session before being handed over to a new network slice.

701 Action

512 512 512 512 a b a b The communications devices,, such as the first communications deviceand the second communications device, may each register in the core network, such as in the 5GC, e.g., according to 3gpp TS 23.502 v. 17.1.0.

702 Action

512 512 a b The communications device,may establish a first default data session, such as a PDU IMS session, i.e., a PDU session for IMS, e.g., in accordance with 3gpp TS 23.502 v. 17.1.0.

512 1 1 506 1 506 1 1 512 512 512 506 1 702 703 a c a b a a a b b a In particular, the first communications devicemay establish the default data session on the first network slice NSidentified by the first network slice identifier S-NSSAI_. The first session management node_handles the default data session. The first user plane node_and a first network address IPis allocated to the first communications device. The default data session between the communications device,and the first user plane node_is illustrated with a solid line between actionand action.

500 a A default service session is established over the default data session with the first communications network. For example, a default IMS session may be established over the default PDU session for IMS.

703 Action

512 512 a b The communications device,registers in IMS, e.g., according to 3gpp TS 23.228 v. 17.1.0 and TS 24.229 v. 17.3.1.

512 521 1 521 1 523 1 a a a a In particular, the first communications deviceregisters with the first application node. The first application nodereserves media resources in the first access gateway.

701 703 512 512 512 a b a. 7 a FIG. Actionstoare valid for both the originating side and the terminating side. Thus, both the first communications deviceand the second communications deviceperform these actions. However,only illustrates them for the first communications device

704 Action

512 512 512 512 512 512 512 512 523 1 523 512 523 512 a b a b a b a b a b b b b The communications device,establishes a dedicated IMS session established over a dedicated data session, such as a dedicated PDU IMS session, with another communications device,. For example, the first communications deviceestablishes the dedicated IMS session with the second communications device. Each communications device,establishes its own data session. The IMS session is established over the respective data session. The establishment of the PDU IMS session includes establishing a media path via the first access gatewayand a third access gatewayassociated with the second communications device. The third access gatewayof the second communications devicemay be implemented as an ATGW.

705 Action

512 512 512 512 523 1 523 512 a b a b a b b. When the service session is set up between the communications devices,the media flows between the communications devices,. The media flow is shown with thick double-headed arrows after successful step up. The media of the IMS session, which is carried by the PDU IMS session, passes through the first access gatewayand the third access gatewayassociated with the second communications device

7 b FIG. illustrates a call flow for initiating the seamless handover of the service session to another network slice.

706 Action

512 2 506 2 512 2 506 2 706 707 a c a a b a b. 7 FIG. The first communications deviceestablishes a new second default data session, such as a second default IMS PDU session, using a second network slice identifier S-NSSAI_and a second session management node_. The first communications deviceis now allocated a second network address IP, such as a second IP address, and the media flow for the second default data session goes through the second user plane node_. The media flow for the second default data session is illustrated with a solid line between actionsandin

500 a A second default service session is established over the second default data session with the first communications network. For example, a second default IMS session may be established over the second default PDU session for IMS.

707 Action

512 521 2 506 2 a a b a The first communications deviceIMS registers with the second application nodevia the second user plane node_.

708 Action

512 2 a The first communications deviceinitiates the transfer of the ongoing IMS session from the first default PDU session to a second default PDU session over the second network slice NS. This triggers the next action.

709 a Action

512 521 1 2 2 512 521 2 a a a a The first communications devicesends a SIP INFO message to the first application nodeto enable setting up the necessary network resources of the second network slice NSfor the IMS session to be transferred between the network slices. The SIP INFO message comprises: the second network address IPof the first communications device, a network address of the second application node, and a session identifier of the first dedicated service session, such as an IMS SIP Session ID of the first dedicated service session. Other information may be possible to include as well, such as charging node, IMS Public Identifier.

709 b Action

521 1 512 a a The first application nodemay acknowledge the reception of the SIP INFO message by responding to the first communications devicewith a SIP 200 OK message.

7 c FIG. illustrates a call flow for completing the seamless handover of the service session to another network slice.

710 a Action

521 1 521 2 2 512 521 1 521 2 523 512 521 2 512 a a a a a b b a b. The first application nodesends a SIP MESSAGE to the second application node. The SIP MESSAGE includes the second network address IPof the first communications device, an IMS SIP session UE context stored in the first application nodeto enable the second application nodeto have the complete IMS session info, and a network address of the third access gatewayassociated with the second communications device. This is done in order to enable the second application nodeto perform network resource reservation for the media and establish the media path with the remote target communications device, such as the second communications device

521 1 a The first application nodemay further send other addressing information for the media, such as charging node, IMS Public Identifier.

710 b Action

521 2 521 1 a a The second application nodemay acknowledge the reception of the SIP message by responding to the first application nodewith a SIP 200 OK message.

711 Action

521 2 a The second application nodestores the IMS PDU session context.

521 2 523 2 521 2 523 2 a a a a The second application nodereserves the necessary network resources for the media in the second access gatewayfor the IMS session to be transferred. In other words, the second application nodefurther sets up the network resources for the media: an ingress network address and an egress network address of the second access gateway.

521 2 523 2 512 523 2 a a a a The second application nodeconnects the egress network address of the second access gatewaytowards the second network address of the first communications device, for a predetermined, preferably short, time. If media is not received on the second service session, that is on the egress and/or ingress network address of the second access gatewaywithin that time the second service session may be abandoned.

712 a Action

521 2 521 1 523 2 521 1 512 a a a a a. The second application nodesends to the first application nodea SIP MESSAGE with the information about the network address of the second access gateway, that is the ingress address and the egress address. This is done in order for the first application nodeto be able to forward this information to the first communication device

712 b Action

521 1 521 2 a a The first application nodemay acknowledge the reception of the SIP message by responding to the second application nodewith a SIP 200 OK message.

713 Action

521 2 512 512 512 521 2 a b a a a The second application nodeestablishes a timer to ensure that the established media path between the second communications deviceand the first communications deviceis used within a certain time. If the first communications deviceabandons the IMS session or something goes wrong, the second application nodemay undo the established network resource reservation for the media such that it is not accessible to other parties.

521 2 a The second application nodestarts the timer for media flow to start.

714 a Action

521 1 512 523 2 512 2 a a a a The first application nodesends a SIP INFO message to the first communications devicewith information about the network address of the second access gateway, that is the ingress address and the egress address. This enables the first communications deviceto send media over the second service session on the second network slice NS, that is over the second media path.

714 b Action

512 521 1 a a The first communications devicemay acknowledge the reception of the SIP message by responding to the first application nodewith a SIP 200 OK message.

715 a Action

512 523 2 521 1 a a a The first communications deviceinitiates the final media transfer by sending a SIP UPDATE, comprising the egress network address of the second access gateway, to the first application node.

715 b Action

521 1 512 a a The first application nodemay acknowledge the reception of the SIP UPDATE by responding to the first communications devicewith a SIP 200 OK message.

716 a Action

521 1 523 2 523 512 512 523 2 a a b b a a The first application nodesends a SIP UPDATE, comprising the egress network address of the second access gateway, to the remote third access gatewayof the second communications device. This is done to update the stored network address of the access gateway of the first communications deviceto match the network address of the second access gateway.

716 b Action

523 521 1 b a The remote third access gatewaymay acknowledge the reception of the SIP message by responding to the first application nodewith a SIP 200 OK message.

717 Action

523 512 523 2 506 2 521 2 521 2 b b a b a a a The media from the remote end starts to go through the new media path which is via the third access gatewayof the second communications device, the second access gatewayand the second user plane node_. The second application nodestops the timer, after media is detected and reported to second application node.

IMS session transfer is complete.

512 1 2 a The first communications deviceshould handle the short transition between the network slices and be able to ensure the media is continuous while it handles both the media on the first network address IPand the second network address IP.

Note that while SIP has been used above as an example of the messaging between the application nodes for transferring the above-described information, other protocols may be used to transfer this information.

8 10 FIGS.- 5 5 a b FIGS.and 8 10 FIGS.- 8 10 FIGS.- 512 521 1 521 2 a a a Exemplifying methods according to embodiments herein will now be described with reference to flowcharts ofand with further reference to. The flowcharts ofcomplement the above-described signalling diagrams and describe exemplifying methods according to embodiments herein from a node perspective. Thus,describe methods performed by the first communications device, and the first and second application nodes,.

The methods are for controlling a service session handover between network slices.

520 520 512 512 a b a b In some embodiments the application network,is an Internet Protocol-based multimedia system, such as IMS, providing the service to the communications devices,, such as providing a media of a media type. Thus, the first and second dedicated service sessions may each be a dedicated IMS session. The first and second default service sessions may each be a default IMS session.

Media types of the service sessions may, for example, be any one or more out of: voice, video, real-time gaming, Virtual Reality, VR, Augmented Reality, AR, and Mixed Reality, MR. In general, the service session may be a real-time service session. The data sessions may be real-time data sessions.

The methods comprises one or more of the following actions, which actions may be taken in any suitable order.

8 FIG. 512 a. illustrates example methods performed by the first communications device

500 As mentioned above, the communications networkmay be a 5G network.

520 a The application layer systemmay be an Internet Protocol, IP, Multimedia Subsystem, IMS. The data session may be a PDU session for IMS.

801 Action

512 1 500 1 1 1 512 521 1 520 523 1 520 a a a a a a The first communications deviceestablishes the first default data session on the first network slice NSof the communications networkbased on the first network slice identifier S-NSSAI_of the first network slice NSsuch that the first network address IPof the first communications device, the first application nodeof an application layer system, and the first access gatewayof the application layer systemis associated with the first default data session.

801 702 7 FIG. a. Actionis related to actionof

802 Action

512 512 1 a b The first communications deviceestablishes an associated first dedicated service session with the second communications deviceover the first dedicated data session based on the first default data session on the first network slice NS.

802 704 7 FIG. a. Actionis related to actionof

803 Action

512 2 1 a The first communications devicemay want to transfer services established over the first dedicated data session to the second network slice NS, for example so that it may terminate the first network slice NS.

512 2 500 2 2 2 512 521 2 520 522 2 520 a a a a a a Therefore, the first communications deviceestablishes the second default data session on the second network slice NSof the communications networkbased on the second network slice identifier S-NSSAI_of the second network slice NSsuch that the second network address IPof the first communications device, the second application nodeof the application layer system, and the second access gateway_of the application layer systemis associated with the second default data session.

500 a The second default service session may be established over the second default data session with the first communications network. For example, a second default IMS session may be established over the second default PDU session for IMS.

521 2 521 1 a a In some embodiments the second application nodeis the same application node as the first application node.

1 2 512 a. The first and second network slice identifiers S-NSSAI_, S-NSSAI_may both be part of an access network subscription profile of the first communications device

803 706 7 FIG. b. Actionis related to actionof

804 Action

1 2 512 521 1 a a In order to initiate the handover of the first dedicated service session from the first network slice NSto the second network slice NSthe first communications devicethen sends a session controlling message to the first application node. The session controlling message controls the service session. The controlling message may be a SIP message. Generally, in embodiments herein different session controlling messages may be implemented with different SIP messages.

2 512 521 2 522 2 512 512 2 1 2 a a a a b The session controlling message comprises: the second network address IPof the first communications device, the network address of the second application node, and the session identifier of the first dedicated service session, to enable reserving network resources of the second access gateway_for the second dedicated service session between the first communications deviceand the second communications deviceestablished over the second dedicated data session based on the second default data session on the second network slice NS, such that handover of the first dedicated service session between the first network slice NSand the second network slice NSis enabled.

522 2 2 a The network resources of the second access gateway_may comprise an ingress network address and an egress network address for the second dedicated service session on the second network slice NS.

The respective first and second default data session may be a default PDU session for IMS. The respective first and second dedicated data session may be a dedicated PDU session for IMS. The respective first and second dedicated service session may be a dedicated IMS session established over the associated first and second dedicated PDU session. The network address may be an IP address. The session identifier may be an IMS SIP session identifier for identifying the first dedicated service session. The transmitted session controlling message may be a SIP INFO message comprising the IMS SIP session identifier of the dedicated IMS session.

804 709 7 FIG. b. Actionis related to actionsof

805 Action

512 521 1 522 2 522 2 522 2 512 522 2 2 a a a a a a a The first communications devicemay receive, from the first application node, a second session controlling message with information related to the network resources of the second access gateway_. The network resources of the second access gateway_comprises an egress network address of the second access gateway_. The first communications devicemay receive the information related to the network resources of the second access gateway_for controlling the second dedicated service session on the second network slice NS.

The second session controlling message may be a SIP INFO message.

805 714 7 FIG. c. Actionis related to actionof

806 Action

512 521 1 522 2 a a a The first communications devicemay send a third session controlling message to the first application nodecomprising the egress network address of the second access gateway_to initiate the handover of the service session, that is to initiate the media transfer.

The third session controlling message may be a SIP UPDATE message.

806 715 7 FIG. c. Actionis related to actionof

9 FIG. 521 1 520 a a illustrates example methods, performed by the first application nodeof an application layer systemcontrolling data sessions, for controlling the service session handover between network slices.

520 a In some embodiments herein the application layer systemis an IMS, the respective data session is a PDU session for IMS, and the context of the first dedicated service session is an established IMS Session context.

The method comprises one or more or the following actions.

901 Action

521 1 512 512 512 1 500 a a b a The first application nodeestablishes the first dedicated service session between the first communications deviceand the second communications deviceover the first default data session of the first communications deviceon the first network slice NSof the communications network.

901 704 7 FIG. a. Actionis related to actionof

902 Action

521 1 512 2 512 522 2 512 2 500 522 2 512 512 1 2 a a a a a a a b The first application nodereceives, from the first communications device, a session controlling message comprising: the second network address IPof the first communications device, the network address of the second application node_associated with the second default data session of the first communications deviceestablished over the second network slice NSof the communications network, and the session identifier of the first dedicated service session, to enable reserving network resources of the second access gateway_for the second dedicated service session between the first communications deviceand the second communications devicesuch that handover of the first dedicated service session between the first network slice NSand the second network slice NSis enabled.

902 709 7 FIG. b. Actionis related to actionof

903 Action

521 1 521 2 805 521 1 a a a Based on the contents of the received session controlling message, the first application nodesends the second session controlling message to the second application node. Note that this is not the same second controlling message as in action. This is the second session controlling message that is handled by the first application node.

2 512 a, a) the second network address IPof the first communications device b) a context of the first dedicated service session, 522 512 b b. c) the network address of an access gateway_serving the second communications device The second session controlling message comprises:

521 1 521 2 521 2 512 512 512 1 2 a a a b a b The first application nodesends the second session controlling message to the second application nodeto enable the second application nodeto perform network resource reservation and establish a data path with the second communications devicefor the second dedicated service session between the first communications deviceand the second communications device, such that handover of the first dedicated service session between the first network slice NSand the second network slice NSis enabled.

The second session controlling message may further comprise other network address information related to a data path of the second dedicated service session.

903 710 7 FIG. c. Actionis related to actionof

904 Action

521 1 521 2 522 2 a a a The first application nodemay receive, from the second application node, a third session controlling message with information related to the reserved network resources of the second access gateway_.

904 712 7 FIG. c. Actionis related to actionof

905 Action

521 1 512 522 2 a a a The first application nodemay send a fourth session controlling message to the first communications devicewith the received information related to the reserved network resources of the second access gateway_.

905 714 7 FIG. c. Actionis related to actionof

906 Action

521 1 512 522 2 715 a a a a 7 c FIG. The first application nodemay further receive, from the first communications device, a fifth session controlling message comprising an egress network address of the second access gateway_. This corresponds to stepin

907 Action

521 1 523 512 512 522 2 512 523 2 523 512 716 a b b a a a a b b a c. 7 FIG. In some embodiments the first application nodesends a sixth session controlling message to the third access gatewayserving the second communications deviceto update a stored network address of an access gateway associated with the first communications deviceto match the network address of the second access gateway_to enable the media to be connected to the first communications device. For example, the sixth session controlling message may be a SIP UPDATE, comprising the egress network address of the second access gateway, to the remote third access gatewayof the second communications device. This corresponds to stepin

10 FIG. 521 2 520 1 2 a a illustrates example methods, performed by the second application nodeof the application layer systemcontrolling data sessions, for controlling a dedicated service session handover between the first network slice NSand the second network slice NS. For example, handover between two IMS sessions may be controlled. The two IMS sessions may be established over two different PDU sessions for IMS that are using different network slices.

512 512 512 1 500 1 2 1 1 512 521 1 520 522 1 520 a b a a a a a a a The method is at least partly performed during the first dedicated service session between the first communications deviceand the second communications deviceover the first dedicated data session based on the first default data session of the first communications deviceon the first network slice NSof the communications networkcomprising the first and the second network slices NS, NS. The first default service session is based on the first network slice identifier S-NSSAI_such that the first network address IPof the first communications device, the first application nodeof the application layer system, and the first access gatewayof the application layer systemis associated with the first default data session.

1001 1003 512 512 a b. For example, actionstobelow may be performed during the first dedicated service session between the first communications deviceand the second communications device

The methods comprise one or more or the following actions.

1001 Action

521 2 512 520 2 2 512 521 2 522 2 a a a a a a The second application noderegisters the first communications devicein the application layer systemfor the second default service session to be established over the second default data session, based on the second network slice identifier S-NSSAIsuch that the second network address IPof the first communications device, the second application node, and the second access gateway_is associated with the second default service session.

1001 707 7 FIG. b. Actionis related to actionof

1002 Action

521 2 521 1 1 a a 2 512 a; a) the second network address IPof the first communications device b) the context of the first dedicated service session; and 522 512 b b. c) the network address of an access gatewayserving the second communications device The second application nodereceives, from the first application nodeassociated with the first network slice NSand controlling the first dedicated data session, a session controlling message comprising:

521 2 521 2 512 512 512 1 2 a a b a b The second application nodereceives the session controlling message to enable the second application nodeto perform network resource reservation and establish the data path with the second communications devicefor the second dedicated service session between the first communications deviceand the second communications device, such that handover of the first dedicated service session between the first network slice NSand the second network slice NSis enabled.

1002 710 7 FIG. c. Actionis related to actionof

1003 Action

521 2 a In some embodiments the second application nodestores the context of the first dedicated service session.

1003 711 7 FIG. c. Actionis related to actionof

1004 Action

521 2 522 2 a a The second application nodereserves network resources of the second access gateway_for the first dedicated service session to be transferred to the second dedicated service session. The reservation is based on the received session controlling message.

1101 711 7 FIG. c. Actionis related to actionof

1005 Action

521 2 522 2 521 1 a a a The second application nodesends a second session controlling message, with information related to the reserved network resources of the second access gateway_, to the first application node.

1102 712 7 FIG. c. Actionis related to actionof

1006 Action

521 2 522 2 2 512 a a a The second application nodemay then connect an egress network address of the second access gateway_towards the second network address IPof the first communications device, for a predetermined time.

1001 711 7 FIG. c. Actionis related to actionof

1007 Action

521 2 a In some embodiments the second application nodestarts a timer for the predetermined time.

1002 713 7 FIG. c. Actionis related to actionof

1008 a Action

521 2 1007 521 2 a a If the second application nodestarted the timer in actionabove, then the second application nodemay stop the timer if data is received over the second dedicated service session within the predetermined time.

1008 717 a c. 7 FIG. Actionis related to actionof

1008 b Action

521 2 523 2 a a In some embodiments the second application nodeabandons the reserved resources for the second dedicated service session if data is not received over the second dedicated service session within the predetermined time. That is, IP ingress and IP egress of the second access gatewaymay be abandoned.

11 FIG. 512 512 a a illustrates a schematic block diagram of embodiments of the first communications device. The first communications devicemay be adapted to control the dedicated service session handover between network slices.

512 1101 1101 1110 a The first communications devicemay comprise a processing modulefor performing the above method actions. The processing modulemay comprise an establishing moduleto, e.g. establish different data session.

512 1110 1 500 1 1 512 521 1 520 522 1 520 a a a a a a a Thus, the first communications deviceis configured to, e.g. by means of the establishing module, establish the first default data session on the first network slice NSof the communications networkbased on the first network slice identifier S-NSSAI_of the first network slice NS, such that the first network address of the first communications device, the first application nodeof the application layer system, and the first access gatewayof the application layer systemis associated with the first default data session.

512 1110 512 1 a b The first communications deviceis further configured to, e.g. by means of the establishing module, establish the associated first dedicated service session with the second communications deviceover the first dedicated data session based on the first default data session on the first network slice NS.

512 1110 2 500 2 2 2 512 521 2 520 522 2 520 a a a a a a a The first communications deviceis further configured to, e.g. by means of the establishing module, establish the second default data session on the second network slice NSof the communications networkbased on the second network slice identifier S-NSSAI_of the second network slice NS, such that the second network address IPof the first communications device, the second application nodeof the application layer system, and the second access gateway_of the application layer systemis associated with the second default data session.

1201 1120 512 1120 521 1 2 512 522 2 512 512 1 2 a a a a a b The processing modulemay comprise a sending moduleto, e.g. send different messages. Thus, the first communications deviceis configured to, e.g. by means of the sending module, send the session controlling message to the first application node. The session controlling message comprises: the second network address IPof the first communications device, the network address of the second application node, and the session identifier of the first dedicated service session, to enable reservation of network resources of the second access gateway_for the second dedicated service session between the first communications deviceand the second communications deviceestablished over the second dedicated data session based on the second default data session on the second network slice, such that handover of the first dedicated service session between the first network slice NSand the second network slice NSis enabled.

1201 1130 512 1130 521 1 522 2 522 2 a a a a The processing modulemay comprise a receiving module. Thus, the first communications deviceis configured to, e.g. by means of the receiving module, receive the second session controlling message from the first application node. The second session controlling message comprises information related to the network resources of the second access gateway_, comprising an egress network address of the second access gateway_, for control of the second dedicated service session on the second network slice.

512 1120 521 1 522 2 a a a The first communications devicemay be configured to, e.g. by means of the sending module, send the third session controlling message to the first application nodecomprising the egress network address of the second access gateway_to initiate the handover of the service session.

12 FIG. 521 1 520 a a illustrates a schematic block diagram of embodiments of the first application nodeof the application layer systemcontrolling data sessions, for controlling the service session handover between network slices.

521 1 1201 1201 1210 a The first application nodemay comprise a processing modulefor performing the above method actions. The processing modulemay comprise an establishing moduleto, e.g. establish the service session, such as an IMS session.

512 512 1210 512 512 512 1 500 a b a b a a. Thus, the communications device,is configured to, e.g. by means of the establishing module, establish the first dedicated service session between the first communications deviceand the second communications devicebased on the first default data session of the first communications deviceon the first network slice NSof the communications network

1301 1220 The processing modulemay comprise a receiving moduleto, e.g. receive different messages.

521 1 1220 512 2 512 522 2 512 2 500 522 2 512 512 1 2 a a a a a a a a b Thus, the first application nodeis configured to, e.g. by means of the receiving module, receive, from the first communications device, a session controlling message comprising: the second network address IPof the first communications device, the network address of the second application node_associated with the second default data session of the first communications deviceestablished over the second network slice NSof the communications network, and the session identifier of the first dedicated service session, to enable reservation of network resources of the second access gateway_for the second dedicated service session between the first communications deviceand the second communications devicebased on the second default data session, such that handover of the first dedicated service session between the first network slice NSand the second network slice NSis enabled.

521 1 1230 a The first application nodemay comprise a sending module.

521 1 1230 521 2 a a 2 512 a, a) the second network address IPof the first communications device b) the context of the first dedicated service session, 522 512 521 2 512 512 512 1 2 b b a b a b c) the network address of an access gateway_serving the second communications device, to enable the second application nodeto perform network resource reservation and establish the data path with the second communications devicefor the second dedicated service session between the first communications deviceand the second communications device, such that handover of the first dedicated service session between the first network slice NSand the second network slice NSis enabled. The first application nodeis further configured to, e.g. by means of the sending module, send the second session controlling message to the second application nodebased on the contents of the received session controlling message. That is, the second session controlling message may be sent in response to the received session controlling message, and the contents of the second session controlling message may be based on the contents of the received session controlling message. The second session controlling message comprises:

521 1 1220 521 2 522 2 a a a The first application nodemay further be configured to, e.g. by means of the receiving module, receive from the second application node, the third session controlling message with information related to the reserved network resources of the second access gateway_.

521 1 1230 512 522 2 a a a Then the first application nodemay further be configured to, e.g. by means of the sending module, send the fourth session controlling message to the first communications devicewith the received information related to the reserved network resources of the second access gateway_.

521 1 1220 512 522 2 a a a The first application nodemay further be configured to, e.g. by means of the receiving module, receive from the first communications device, the fifth session controlling message comprising an egress network address of the second access gateway_.

521 1 1230 512 512 522 2 a b a a Then the first application nodemay further be configured to, e.g. by means of the sending module, send the sixth session controlling message to the access gateway, adapted to serve the second communications device, to update the stored network address of an access gateway associated with the first communications deviceto match the network address of the second access gateway_.

520 a In some embodiments the application layer systemis an IMS, the data session is a PDU session for IMS, and the context of the first dedicated service session is an IMS session context of the dedicated IMS session.

In some other embodiments the second session controlling message further comprises other network address information related to the data path of the second dedicated service session.

13 FIG. 521 2 520 1 2 a a illustrates a schematic block diagram of embodiments of the second application nodeof the application layer system, for controlling the dedicated service session handover between the first network slice NSand the second network slice NS,

512 512 512 1 500 1 2 1 1 512 521 1 520 522 1 520 a b a a a a a a a The service session handover is the handover of the first dedicated service session between the first communications deviceand the second communications device. The first dedicated service session is established over the first dedicated data session. The first dedicated data session is based on the first default data session of the first communications deviceon the first network slice NSof the communications networkcomprising the first and the second network slices NS, NS. The first default data session is based on the first network slice identifier S-NSSAI_such that the first network address IPof the first communications device, the first application nodeof the application layer system, and the first access gatewayof the application layer systemis associated with the first default data session.

521 2 1301 1301 1310 520 a a. The second application nodemay comprise a processing modulefor performing the above method actions. The processing modulemay comprise a registering moduleto, e.g. register communications devices in the application layer system

521 2 1310 512 520 2 2 512 521 2 522 2 a a a a a a Thus, the second application node_is configured to, e.g. by means of the registering module, register the first communications devicein the application layer systemfor the second default service session to be established over the second default data session, based on the second network slice identifier S-NSSAIsuch that the second network address IPof the first communications device, the second application node, and the second access gateway_is associated with the second default service session.

1301 1320 521 521 1320 521 1 1 a b a 2 512 a; a) the second network address IPof the first communications device b) the context of the first dedicated service session; 522 512 b b, c) the network address of an access gatewayserving the second communications device 521 2 512 512 512 1 2 a b a b to enable the second application nodeto perform network resource reservation and establish the data path with the second communications devicefor the second dedicated service session between the first communications deviceand the second communications device, such that handover of the first dedicated service session between the first network slice NSand the second network slice NSis enabled. The processing modulemay further comprise a receiving module. Thus, the application node,is configured to, e.g. by means of the receiving module, receive, from the first application nodeassociated with the first network slice NSand controlling the first dedicated service session, the session controlling message comprising:

1301 1330 521 2 1330 522 2 a a The processing modulemay further comprise a reserving module. Thus, the second application node_is configured to, e.g. by means of the reserving module, reserve network resources of the second access gateway_for the first dedicated service session to be transferred to the second dedicated service session based on the received session controlling message.

1301 1340 521 2 1340 521 1 522 2 a a a The processing modulemay further comprise a sending module. The second application node_is configured to, e.g. by means of the sending module, send to the first application nodethe second session controlling message with information related to the reserved network resources of the second access gateway_.

521 2 1302 a The second application node_may further comprise a memory.

521 2 1302 a In some embodiments the second application node_is configured to, e.g. by means of the memory, store the context of the first dedicated service session.

1301 1350 521 2 1350 522 2 2 512 a a a The processing modulemay further comprise a connecting module. In some embodiments the second application node_is configured to, e.g. by means of the connecting module, connect an egress network address of the second access gateway_towards the second network address IPof the first communications device, for the predetermined time.

1301 1360 521 2 1360 a The processing modulemay further comprise a timer module. In some embodiments the second application node_is configured to, e.g. by means of the timer module, start the timer for the predetermined time.

521 2 1360 a The second application node_may further be configured to, e.g. by means of the timer module, stop the timer if data is received over the second dedicated service session within the predetermined time.

521 2 1330 a In some embodiments the second application node_is configured to, e.g. by means of the reserving module, abandon the reserved resources for the second dedicated service session if data is not received over the second dedicated service session within the predetermined time.

512 521 1 521 2 1106 1206 1306 a a a The first communications device, and the first and second application nodes,may comprise a respective input and output unit,,, andconfigured to communicate with each other. The input and output unit may comprise a receiver (not shown) and a transmitter (not shown).

1104 1204 1304 512 521 1 521 2 512 521 1 521 2 512 521 1 521 2 a a a a a a a a a 11 13 FIGS.- The embodiments herein may be implemented through a respective processor or one or more processors, such as the respective processing circuit,, andin the first communications device, and the first and second application nodes,depicted in, together with computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the respective the first communications device, and the first and second application nodes,. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server or a cloud and downloaded to the first communications device, and the first and second application nodes,.

512 521 1 521 2 1102 1202 1302 512 521 1 521 2 a a a a a a The first communications device, and the first and second application nodes,may further comprise a respective memory,, andcomprising one or more memory units. The memory comprises instructions executable by the processor in the first communications device, and the first and second application nodes,.

1202 1302 1402 1502 512 521 1 521 2 a a a Each respective memory,,andis arranged to be used to store e.g. information, data, configurations, and applications to perform the methods herein when being executed in the first communications device, and the first and second application nodes,.

1103 1203 1303 512 521 1 521 2 a a a In some embodiments, a respective computer program,, andcomprises instructions, which when executed by the at least one processor, cause the at least one processor of the respective first communications device, and the first and second application nodes,to perform the actions above.

1105 1205 1305 In some embodiments, a respective carrier,, andcomprises the respective computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

512 521 1 521 2 a a a Those skilled in the art will also appreciate that the modules and units described above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the respective first communications device, and the first and second application nodes,, that when executed by the respective one or more processors such as the processors described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).

14 15 FIGS.and Note that there are no.

16 FIG. 3210 3211 3214 3211 3212 3212 3212 111 112 3213 3213 3213 3212 3212 3212 3214 3215 3291 3213 3212 3292 3213 3212 3291 3292 3212 a b c a b c a b c c c a a With reference to, in accordance with an embodiment, a communication system includes a telecommunication network, such as a 3GPP-type cellular network, which comprises an access network, such as a radio access network, and a core network. The access networkcomprises a plurality of base stations,,, such as the source and target access node,, AP STAs NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area,,. Each base station,,is connectable to the core networkover a wired or wireless connection. A first user equipment (UE) such as a Non-AP STAlocated in coverage areais configured to wirelessly connect to, or be paged by, the corresponding base station. A second UEsuch as a Non-AP STA in coverage areais wirelessly connectable to the corresponding base station. While a plurality of UEs,are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station.

3210 3230 3230 3221 3222 3210 3230 3214 3230 3220 3220 3220 3220 The telecommunication networkis itself connected to a host computer, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computermay be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections,between the telecommunication networkand the host computermay extend directly from the core networkto the host computeror may go via an optional intermediate network. The intermediate networkmay be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network, if any, may be a backbone network or the Internet; in particular, the intermediate networkmay comprise two or more sub-networks (not shown).

16 FIG. 17 FIG. 3291 3292 121 3230 3250 3230 3291 3292 3250 3211 3214 3220 3250 3250 3212 3230 3291 3212 3291 3230 3300 3310 3315 3316 3300 3310 3318 3318 3310 3311 3310 3318 3311 3312 3312 3330 3350 3330 3310 3312 3350 The communication system ofas a whole enables connectivity between one of the connected UEs,such as e.g. the UE, and the host computer. The connectivity may be described as an over-the-top (OTT) connection. The host computerand the connected UEs,are configured to communicate data and/or signaling via the OTT connection, using the access network, the core network, any intermediate networkand possible further infrastructure (not shown) as intermediaries. The OTT connectionmay be transparent in the sense that the participating communication devices through which the OTT connectionpasses are unaware of routing of uplink and downlink communications. For example, a base stationmay not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computerto be forwarded (e.g., handed over) to a connected UE. Similarly, the base stationneed not be aware of the future routing of an outgoing uplink communication originating from the UEtowards the host computer. Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to. In a communication system, a host computercomprises hardwareincluding a communication interfaceconfigured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system. The host computerfurther comprises processing circuitry, which may have storage and/or processing capabilities. In particular, the processing circuitrymay comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computerfurther comprises software, which is stored in or accessible by the host computerand executable by the processing circuitry. The softwareincludes a host application. The host applicationmay be operable to provide a service to a remote user, such as a UEconnecting via an OTT connectionterminating at the UEand the host computer. In providing the service to the remote user, the host applicationmay provide user data which is transmitted using the OTT connection.

3300 3320 3325 3310 3330 3325 3326 3300 3327 3370 3330 3320 3326 3360 3310 3360 3325 3320 3328 3320 3321 3300 3330 3335 3337 3370 3330 3335 3330 3338 3330 3331 3330 3338 3331 3332 3332 3330 3310 3310 3312 3332 3350 3330 3310 3332 3312 3350 3332 3310 3320 3330 3230 3212 3212 3212 3291 3292 17 FIG. 17 FIG. 17 FIG. 16 FIG. 17 FIG. 16 FIG. a b c The communication systemfurther includes a base stationprovided in a telecommunication system and comprising hardwareenabling it to communicate with the host computerand with the UE. The hardwaremay include a communication interfacefor setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system, as well as a radio interfacefor setting up and maintaining at least a wireless connectionwith a UElocated in a coverage area (not shown in) served by the base station. The communication interfacemay be configured to facilitate a connectionto the host computer. The connectionmay be direct or it may pass through a core network (not shown in) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardwareof the base stationfurther includes processing circuitry, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base stationfurther has softwarestored internally or accessible via an external connection.The communication systemfurther includes the UEalready referred to. Its hardwaremay include a radio interfaceconfigured to set up and maintain a wireless connectionwith a base station serving a coverage area in which the UEis currently located. The hardwareof the UEfurther includes processing circuitry, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UEfurther comprises software, which is stored in or accessible by the UEand executable by the processing circuitry. The softwareincludes a client application. The client applicationmay be operable to provide a service to a human or non-human user via the UE, with the support of the host computer. In the host computer, an executing host applicationmay communicate with the executing client applicationvia the OTT connectionterminating at the UEand the host computer. In providing the service to the user, the client applicationmay receive request data from the host applicationand provide user data in response to the request data. The OTT connectionmay transfer both the request data and the user data. The client applicationmay interact with the user to generate the user data that it provides. It is noted that the host computer, base stationand UEillustrated inmay be identical to the host computer, one of the base stations,,and one of the UEs,of, respectively. This is to say, the inner workings of these entities may be as shown inand independently, the surrounding network topology may be that of.

17 FIG. 3350 3310 3330 3320 3330 3310 3350 In, the OTT connectionhas been drawn abstractly to illustrate the communication between the host computerand the use equipmentvia the base station, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UEor from the service provider operating the host computer, or both. While the OTT connectionis active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

3370 3330 3320 3330 3350 3370 The wireless connectionbetween the UEand the base stationis in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UEusing the OTT connection, in which the wireless connectionforms the last segment. More precisely, the teachings of these embodiments may improve the data rate, latency, power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime.

3350 3310 3330 3350 3311 3310 3331 3330 3350 3311 3331 3350 3320 3320 3310 3311 3331 3350 A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connectionbetween the host computerand UE, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connectionmay be implemented in the softwareof the host computeror in the softwareof the UE, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connectionpasses; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software,may compute or estimate the monitored quantities. The reconfiguring of the OTT connectionmay include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station, and it may be unknown or imperceptible to the base station. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer'smeasurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software,causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connectionwhile it monitors propagation times, errors etc.

18 FIG. 16 FIG. 17 FIG. 18 FIG. 3410 3411 3410 3420 3430 3440 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference toand. For simplicity of the present disclosure, only drawing references towill be included in this section. In a first actionof the method, the host computer provides user data. In an optional subactionof the first action, the host computer provides the user data by executing a host application. In a second action, the host computer initiates a transmission carrying the user data to the UE. In an optional third action, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth action, the UE executes a client application associated with the host application executed by the host computer.

19 FIG. 16 FIG. 17 FIG. 19 FIG. 3510 3520 3512 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference toand. For simplicity of the present disclosure, only drawing references towill be included in this section. In a first actionof the method, the host computer provides user data. In an optional subaction (not shown) the host computer provides the user data by executing a host application. In a second action, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third action, the UE receives the user data carried in the transmission.

20 FIG. 16 FIG. 17 FIG. 20 FIG. 3610 3620 3621 3620 3611 3610 3630 3640 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference toand. For simplicity of the present disclosure, only drawing references towill be included in this section. In an optional first actionof the method, the UE receives input data provided by the host computer. Additionally or alternatively, in an optional second action, the UE provides user data. In an optional subactionof the second action, the UE provides the user data by executing a client application. In a further optional subactionof the first action, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third subaction, transmission of the user data to the host computer. In a fourth actionof the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

21 FIG. 32 33 FIGS.and 21 FIG. 3710 3720 3730 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to. For simplicity of the present disclosure, only drawing references towill be included in this section. In an optional first actionof the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second action, the base station initiates transmission of the received user data to the host computer. In a third action, the host computer receives the user data carried in the transmission initiated by the base station.

When using the word “comprise” or “comprising” it shall be interpreted as non-limiting, i.e. meaning “consist at least of”.

The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used.